1. Field of the Invention
The present invention relates to an improvement in a pipe joint construction for enhancing a separation preventive function between a receiving pipe section and an inserted pipe section inserted into and connected to the receiving pipe section from a direction of pipe axis, the pipe sections constituting part of a fluid pipeline system such as a water pipeline system or the like.
2. Description of Related Art
Conventionally, the following techniques have been known as pipe joint construction enhancing the separation preventive function between the receiving pipe section and the inserted pipe section.
(1) The receiving pipe section has, formed on/in inner peripheral surfaces thereof, an annular stopper wall portion for limiting a maximum inserted position (maximum contracting position) between the pipe sections by contacting, in a pipe axis direction, an annular engaging projection protruding from an outer peripheral surface of the inserted pipe section, and a mounting groove for receiving a substantially C-shaped lock member elastically deformable in a diameter-increasing direction.
Cam surfaces are formed on corners, opposing to each other in the pipe axis direction, of the engaging projection of the inserted pipe section and the lock member attached to the mounting groove, for elastically deforming the lock member in the diameter-increasing direction to an inside diameter allowing passage of the inserted pipe section as it is inserted into the receiving pipe section. (see Patent Document 1)
(2) A plurality of circumferential engaging projections protrude radially outward from an outer peripheral surface of the inserted pipe section inserted into and connected to the receiving pipe section from the direction of pipe axis. An annular wall portion is formed on an inner peripheral surface of the receiving pipe section for contacting, in the pipe axis direction, each engaging projection of the inserted pipe section placed in the inserted and connected position, thereby preventing relative disengaging movement of the pipe sections. The annular wall portion includes attachment/detachment recesses formed therein for allowing passage and movement of each engaging projection in the direction of pipe axis only when both the pipe sections are placed in a particular phase. (see Patent Documents 2 and 3)    Patent Document 1: Japanese Patent Publication No. 9-303636    Patent Document 2: Japanese Patent Publication No. 9-292074    Patent Document 3: Japanese Patent Publication No. 2001-263565
In the former conventional pipe joint construction noted above, the lock member mounted in the mounting groove in advance can be deformed by simply inserting the inserted pipe section into the receiving pipe section to increase the inside diameter for allowing passage of the engaging projection as the inserting operation proceeds. As a result, a desired separation preventive function can be performed by contact between the lock member on the side of the receiving pipe section and the engaging projection on the side of the inserted pipe section, while allowing the pipe sections to be connected easily and efficiently.
On the other hand, when a necessity arises to disassemble the pipe sections for maintenance and inspection or for changing of parts, the lock member must be expanded against the elastic force to the extent of allowing the engaging projection of the inserted pipe section to pass, by using a jig inserted through an annular space between the inner peripheral surface of the receiving pipe section and the outer peripheral surface of the inserted pipe section. This involves a great deal of labor and effort in the disassembling operation.
In the latter conventional pipe joint construction noted above, when connecting the receiving pipe section to the inserted pipe section, an adjustment is made for establishing the particular phase where the plurality of engaging projections of the inserted pipe section agree with the plurality of attachment/detachment recesses formed in the annular wall portion of the receiving pipe section. Both the pipe sections are moved toward each other in this state, thereby allowing each engaging projection of the inserted pipe section to pass through each attachment/detachment recess. Then, the pipe sections are rotated relative to each other about the pipe axis to a predetermined attachment position where each engaging projection placed in the attachment/detachment operating position corresponds to an inner surface of the annular wall portion.
Even if a withdrawing force is applied to both the pipe sections in this condition, the engaging projections contact the inner surface of the annular wall portion of the receiving pipe section from the direction of pipe axis, thereby preventing relative disengaging movement between the pipe sections.
Therefore, when necessity arises to disassemble the pipe sections, it is sufficient to rotate both the pipe section relative to each other from the predetermined attachment position to the attachment/detachment operating position and then relatively move and disengage the pipe sections along the direction of pipe axis. As a result, the pipe sections can be disassembled efficiently compared with the former pipe joint construction which requires that the jig is operated in the limited space within the receiving pipe section.
However, in assembling or disassembling the pipe sections, it is required to rotate the heavy pipe sections relative to each other from the attachment/detachment operating position to the predetermined attachment position, or from the predetermined attachment position to the attachment/detachment operating position. Such relative rotating operations disadvantageously requires a great deal of labor.